Cuing apparatus



1962 H. J. SCHLAFLY, JR 3,020,532

CUING APPARATUS 4 Sheets-Sheet 1 Filed NOV. 4, 1957 mOnm NONm ATTORNEYSFeb. 6, 1962 H. J. SCHLAFLY, JR 3,020,532

CUING APPARATUS Filed Nov. 4, 1957 4 Sheets-Sheet 2 13 2 CJ;ER%% L%LY JRclos 005 y I ATTORNEYS Feb. 6, 1962 H. J. SCHLAFLY, JR 3,020,532

CUING APPARATUS 4 Sheets-Sheet 3 Filed Nov. 4, 1957 ..llllllllllllillllll B528 025/ Mmfimmo mam QNQE L mll HUBERT J. SCHLAFLY,JR. I MM M5m- 1 1 N V EN TOR.

ATTORNEYS Ni. u

1962 H. J. SCHLAFLY, JR 3,020,532

CUING APPARATUS Filed Nov. 4; 1957 4 Sheets-Sheet 4 INVENTOR. HUB ERT J.SCHLAFLY,JR.

BY P w, MB -1+ AZTTORNE s United States Patent 3,020,532 CUING APPARATUSI Hubert J. Schlafly, Jr., Hollis, N.Y., assignor to TeleprompterCorporation, New York, N.Y., a corporation of New York Filed Nov. 4,1957, Ser. No. 694,276 18 Claims. (Cl. 340-334) This invention relatesto cuing apparatus and more particularly to a cuing system controllingthe synchronized presentation of a continuously moving script sheet at aplurality of remotely spaced locations. In a cuing system according tothe invention, each of a plurality of script display units includes ascript sheet driven between supply and take-up rolls past a displaystation by a reversible motor. Discontinuities disposed lengthwise ofthe script sheets at the same points in the text thereon effect thegeneration of signals in each of the script display units which are usedto keep the various units in step, so that all will display at any onetime the same line of text. One system for effecting such synchronismamong a plurality of script display units is disclosed in my Patent No.2,765,552. The present invention provides improved means to this end. I

It further provides means whereby the speeds of the driving motors inall display units may be closely matched and simultaneously varied overa wide range, and means for regulating the speed of the individualdisplay units despite variations in load imposed by them on theirrespective drive motors.

The invention will now be further described with reference to theaccompanying drawing in which:

FIG. 1 is a view in front elevation of the components of a cuing systemaccording to the invention including two script display units;

FIGS. 2a and 2b form a schematic diagram of the apparatus of FIG. 1;

FIG. 3 is a diagram of certain wave forms useful in explaining theoperation of the apparatus of FIGS. 2a and 212;

FIG. 4 is a diagram illustrating the interconnection of units accordingto the invention to provide a cuing system including up to six scriptdisplay units, and p FIG. 5 is a diagram illustrating the combination oftwo master control units according to the invention to provide a cuingsystem including up to four display units.

In FIG. 1 a system control unit is generally indicated at 2 coupled bymeans of cables 3 with each of two script display units 4. A handoperated control S and an over-riding hand control unit are also shown,connected by cables 12 and 14 respectively with the control unit 2. Ineach of the display units 4 a script sheet 16 is shown, bearing the textof a speaker, actor or the like. The script sheet is reversibly drivenbetween supply and take-up spools or rolls within the display unit.Electrical discontinuities are provided periodically lengthwise of thescript sheets 16, conveniently one in the same position on each panelthereof, the script sheets being advantageously manufactured infan-folded form with interleaved carbon and copy sheets so that aplurality of sheets 16 may be produced in a single typewriting operaicein the speed of advance of the script sheet of all display units, and atwo position push button switch 20 permits simultaneous reversal of thedirection of travel of the sheet at all display units. The hand controlunit 10 includes the same speed control 13 and reversing switch 20 and,in addition, a switch S502 (FIG. 2a) by means 7 of which the handcontrol ti can be disabled, control of the system being thus seized bythe operator of hand control 10. The selector hand control unit 10 alsoincludes a jack into which can be plugged a cablell terminating at a twoposition switch 13, arranged for foot operation, for example. Thispermits start-stop operation of the system at the speed set on speedcontrol 18 of unit 10.

In the embodiment of the invention illustrated, the control unit 2, withone of the controls 8 and 10, includes the components necessary forsynchronized operation of two display units. The control unit 2 thusincludes certain master control components, for the speed control andsynchronizing functions of a system which may include two or moredisplay units. It also includes two sets of components which may beidentical. Each of these may be termed a set of display unit controlcomponents, each such set supplying the motor power, speed trim andsubordinate synchronizing signals required by one display unit.Additional sets of such display unit control components may be providedin separate chassis, such chassis each advantageously including two suchadditionalsets, for connection by a cable to the unit 2 and to eachother successively in order to permit synchronized operation in thesystem of a number of display units larger than two.

For control of such a system, which in a particular design may includeas many as ten display units, there are provided in the control unit 2certain operating controls in addition to the speed control 18 andreversing switch 20 of the hand control units 3 and 10 already referredto. Referring to FIG. 2a, AC. power for the system is brought to a jack5 on unit 2 through a cable 6 which includes a third conductor forconnection to the building ground of the system ground, e.g. that of thechassis in all of the cable-interconnected units of the system. Thespeed control and reversing switch of the hand controls 8 and 10 are.master controls which atiect all display units in'the system.Additional master controls are indicated in FIG. 1 at 814311, Slim andS103 on the front panel of unit 2. S101 is an on-oif power switch forthe entire system. A panel lamp I161 indicates the position of theswitch SIM and, more particularly, the existence of rectified negativebias voltage produced by unit 2 when switch S101 is closed and the unitis properly operating. I

S102 is a push button synchronizing relay release switch presently to bedescribed. S103 is a switch'controlling operation in all display unitsof lamps for illumination of the script sheet.

, The control unit 2 also includes certain additional controls induplicate, one for each of the two display units controlled by unit 2,these individual controls forming part of the two sets of identicaldisplay unit control components above referred to. To distinguish them,such identical components will hereinafter bear reference characterswhich are the same as to their units and tens digits, but different asto their hundreds digit.

Thus switches S201 and S301 permit individual disconnection of the twodisplay units 4 of FIG. 1 from the system shown in that figure, in theevent of their malfunctioning, for example. The connected ordisconnected state of the individual units 4 is indicated at panel lampsI201 and I301, these lamps being lighted when their respective displayunits are disconnected by setting of the corresponding switches 82M and8301 to the Off position, and also when the motion of the script sheetsin those units respectively is temporarily halted during the periodicsynchronizing operation presently to be described.

Switches S202 and S302 similarly each permit control, at one of theunits of the lamps by means of which the script sheet at such unit isilluminated.

Controls and 308 are provided for operation of potentiometers which makefine adjustments in the speed of travel of the script sheets in the twodisplay units.

Telephone jacks E204 and E304 may be provided to monitor with a meterthe armature current of the script driving motors in the display units.

Referring to FlGS. 2a and 2b, the electrical components of the controlunit 2, display units 4 and hand controls 8 and 10 are indicated atcorrespondingly numbered dash line boxes. The master control componentsof the control unit are those shown in FIG. 2a. In F16. 2b, and Withinthe portion of box 2 in that figure, the sets of components to the leftand right of the dash line AA are identical with each other, with theexception of transformer T201 and relay K201 which are not duplicated tothe right of line AA. Each such set provides, when connected to thecomponents of FIG. 2a, the components necessary to synchronizedoperation of a display unit 4 in conjunction with another unit 4connected to another such set which is in turn connected to thecomponents of FIG. 2a.

In FIG. 2a the main power switch S101 controls the application ofalternating current power, for example that of an ordinary 110 voltlighting circuit, to two condoctors 24 and 26.

In FIG. 2a, conductors 24 and 26 supply power to a transformer T101.They also permit energization of a relay K101 upon closing of switchS502 (which is controlled by control 18 of FIG. 1), to shift control ofthe system from hand control unit to unit 10. A further relay K102providing for maintenance of proper synchronism among the display unitsupon reversal of script travel is energized upon closing of thereversing switch S401 or S501, according as switch S502 is open orclosed. Switches S401 and S501 are coupled to the push buttons 20 ofcontrol units 8 and in FIG. 1 respectively. Master switch S103 for thescript lamps in the display unit is also connected to the conductor 2-1,the lamp circuits of the display units being connected betweenconductors 24 and 26 through this switch.

In FlG. 2b, conductors 24- and 26 energize transformers T201 and T301.These supply power, in a manner presently to be described, to thearmatures of the driving motors 28 in the two display units 4 connectedto control unit 2. Conductors 24 and 26 also energize a transformer T202from which separate rectified direct current voltages are derived forthe field windings 29 of motors 23.

Referring again to FIG. 2a, .a full wave rectifier cornprising diodesZ101 and Z102 connected to the secondary of transformer T101 generates arectified positive 8+ voltage on a conductor 32, filtered at capacitorC101. A second pair of d odes Z103 and Z104 develops a direct currentvoltage on the cathode of a vacuum diode V101A. This voltage isunfiltered and consequently has the shape indicated at wave form A inFIG. 3. A third combination of diodes Z105, Z106, oppositely poled,develops at a conductor 55 a rectified negative B voltage, filtered atcapacitor C102. Lamp 1101 connected from conductor 36 to groundindicates when lighted the existence of negative bias voltage atconductor 30.

A capacitor C104 is connected in series with a resistor R105 betweenconductor 32 and ground, and the vacuum diode V101A has its anodeconnected to the junction of C104 and R105 and its cathode connected toground through a resistor R102, small in comparison to R105.

Capacitor C10 charges exponentially toward the voltage of conductor 32but is discharged at twice the power line frequency when the cathode ofV101A is lowered toward the end of each half cycle of rectificationbelow the voltage at the anode V101A. Consequently the anode of V101Aexhibits a substantially sawtooth voltage wave form as indicated in fulllines at B in FIG. 3, wherein wave form A is reproduced in dash linesfor comparison.

This saw-tooth component is coupled through capacitor C103 to the gridof a cathode follower-connected triode V1013 where it is mixed with aDC. voltage applied to the control grid of V1018 from a potentiometerR401 in the hand control 8 or, alternatively, from a potentiometer R501in hand control 10. The taps on R401 and R501 are mechanically coupledto the speed control knobs 18 of hand controls 8 and 10 of FIG. 1respectively. R401 and R501 are otentiometers in a voltage dividingcircuit extending via R101 and R109 between conductors 32 and 36, one orthe other of R401 and R501 being inserted in this voltage divideraccordingly as relay K101 is de-energized or energized. The range ofvolt-ages available at the taps of R401 and R501 is adjustable at thepotentiometer-connected resistance R101. One or the other of the taps isconnected into the grid circuit of V1018 through contacts of relay K101.The voltage at the cathode of V101B is a composite one, comprising asubstantially saw-toothed component as shown at wave form B of FIG. 3,superimposed on a varying DC. level determined by the setting of R401 orR501.

This composite voltage, provided at low impedance from the cathodefollower source of V1013, is employed to control the ignition phase intwo pairs of grid controlled gas rectifier tubes V201, V202 and V301,V302 which supply armature current from transformers T201 and T301respectively to the script sheet drive motors 28 in the two displayunits 4 shown in FIG. 2b. The range of voltages available at the taps ofR401 and R501 is set at R101 so that, for a range of positions of thosetaps beginning at the ends of R401 and R501 adjacent R109, the voltageon the cathode of V101B produces no conduction in V201, V202 and V301,V302. Under these conditions the script sheets are stationary in thedisplay units.

It may be noted that upon disconnection of the hand controls 8 and 10 attheir cables 12 and 14, the voltage divider circuit including R101 andR109 is opened, returning the grid of the V101B to the voltage ofconductor 36. This cuts oil V101B and holds tubes V201, V202 and V301,V302 entirely nonconducting, so that the script sheet will not move inany of the display units.

For control of the amount of conduction in thyratrons V201, V202 andV301, V302 and hence of the amount of current supplied to the scriptdriving motors, the cathode of V1013 is connected to ground throughidentical voltage dividing circuits in parallel, one for each of thedisplay units 4. One of these circuits includes resistors R211 and R209and a speed control trim potentiometer R200 whose ungrounded end is atthe filtered positive direct current voltage applied to conductor 38 byrectifiers Z201 and Z202 for energization of the field circuit 29 of themotor 28 in the display unit associated with tubes V201, V202. Aparallel resistance capacity combination R201, C201 leads from thejunction of R211 and R209 to the grids of the associated thyratronsV201, V202 through decoupling resistors R202 and R203.

Control of the speed of motors 28 in the display units is effected bycontrol of the voltage at the grids of the thyratrons pairs V201, V202and V301 and V302. This voltage is for each thyratron pair of mixture offour component factors:

(1) A direct current voltage level set at the hand control potentiometerR401 or R501. This voltage is the main speed determining factor and actson all display units.

(2) The saw-tooth voltage in V101A as reproduced in the cathode of:V1013, likewise acting on all display units.

(3) The setting of speed trim potentiometers R208 and R308, individualto the two'display units shown. (4) A regenerative feed-back voltage,individual to each display unit, developed for one display unit at R201,C201 and for the other at R301, C301.

The saw-toothed component of voltage permits the phase at which thetubes V201, V202 and V301, V302 begin to conduct to be controlled or setto any point within the positive half cycle of the A.C. voltage appliedby transformers T201 and T301 to the anodes of those tubes. This isillustrated for one of these tubes at wave form C in FIG. 3, where theA.C. Voltage at the thyratron plate is indicated at 40, thecorresponding minimum grid ignition voltage at 42, and the mixedsaw-tooth and DC. voltage 0 from V101B at 44 and 44 for two values ofDC. component. For a grid voltage 44 the conduction phase amounts toalmost 90 of the A.C. cycle, whereas for grid voltage 44' it amounts toperhaps 45. The phase at which conduction is initiated is the same forboth thyratrons of each pair and this phase controls the amount ofcurrent supplied to the motor armature, supply being made through achoke L201 and across capacitor C202B for one display unit 4. Thus thespeed of motors 28 in both display units is basically controlled by thatone of potentiometers R401 and R501 which, according to the conditionofoverriding switch 22 (S502) in hand control and according to theconsequent condition of relay K101, is connected to the grid of V1013. I

To compensate for inequalities characteristic of dilferent displayunits, for example of the friction in their supply and take-up spoolsand also to compensate for inequalities among the motor armature supplythyratrons, the trimming potentiometers R208 and R308 are supplied. Theeffect of these potentiometers is to change the DC. level at the gridsof the associated thyratrons as necessary to compensate for anyinequalities.

The RC. circuits R201, C201 and R301, C301 form each a regenerativefeed-back circuit which produces a very high degree of regulation inmotor speed in the face of changes in motor load and of the armaturecurrent drawn in consequence thereof.

With increase in current drawn by the motor armature in a display unit4, for example the one to the left in FIG. 2b, capacitor C201 acquiresan increasing charge, with the terminal thereof adjacent the thyratrongrids at positive polarity with respect to the opposite terminal, thischarge being the result of the increased ionization produced in the tubeby the heavier current flowing therein. This charge raises the netvoltage of the combined sawtooth and DC. Wave form, and its appearanceat the grid of its associated thyratrons causes conduction to beginearlier in those tubes. Consequently the power delivered to the motor isincreased, as is required to maintain its speed constant in spite of thegreater mechanical load applied thereto.

The charge on capacitor C201 leaks off in part between the successiveone-half cycles of the power line frequency associated with conductionin the two thyratron tubes and this rate of discharge can be controlledby adjustment of potentiometer R201, through which the discharge takesplace. .By adjustment of this potentiometer the rate of discharge can beso set that the drive motor in the display unit will maintainsubstantially constant speed over a very wide range of armaturecurrents.

Otherwise stated, the positive ion grid current which flows duringconduction in the thyratrons V201 and V301 charges condenser C201 to anextent dependent upon and varying directly with average conduction inthose tubes. This charge, raising the potential of the terminal ofcapacitor C201 adjacent the thyratron grids with respect to the oppositeterminal, raises the grid potential in and causes earlier conduction ofthe thyratrons to supply more armature current as demanded by increasedload'on the motor 28.

The operation of R301, C301 and R308in controlling conduction in V301and V302 for speed control of the script in the right hand display unitof FIG. 2b is exactly similar.

Reference has already been made to transformer T202 and its separatefull wave rectifier circuits Z201, Z202 and Z301, Z302 for the fieldwindings 29 in the two display units shown. Connection to the fieldwindings is made from the rectifiers at conductor 38 in one case and atconductor 46 in the other, through the contacts of reversing relay K201.This relay includes contacts for both of the display units controllablefrom control unit 2. The mid-tap of the secondary on transformer T202 isgrounded at the control unit chassis, as is also the case withtransformer T101. Hence, one normally open and one normally closedcontact on relay K201 for each of the display units is connected toground to provide a return path for the field circuit of the associateddisplay circuit, whatever the state of energization of relay K201 andwhatever the consequent direction of current flow through the fieldwindings.

One terminal of the armature in motors 28 is also connected, via cables3 to control unit ground in view of the connection to such ground of themid-tap on the secondary windings of transformers T201 and T301. Thiscontrol unit ground potential is extended to all units of system by thecables which connect them to unit 2.

Conductor 38 with its rectified voltage is extended into FIG. 2a toapply voltage to the actuating coil of a relay K103 forming part of thesynchronizing means whereby the script sheets of the units of the systemare periodically brought back into step, at such frequency in practicethat the maximum departure from synchronism is negligible. The circuitfor energization of relay K103 is completed when tube V102, in seriestherewith, is brought into conduction in a manner presently to heexplained.

According to another feature of the present invention, synchronism isperiodically established among all the display units connected to thecontrol unit 2. In each display unit a conductor 50 is periodicallyconnected to the common system ground by a discontinuity in the scriptsheet. In the embodiment illustrated in the drawings, conductor 50 ineach display unit connects with a brush 52 which makes contact with ametallic idler roller 54 at ground potential, and over which the scriptsheet passes, every time a discontinuity in the form of a hole in thescript sheet passes under the brush. I Brush 52 may be referred to as asynchronizing contact. The discontinuities may, however, be of othertypes. I I

These discontinuities are disposed, as has already been stated, oppositethe same points in the text on the script sheets at all display units.Minor variations in speed of travel of the script sheet. in the variousdisplay units results in the grounding of their contacts 52 at slightlydifferent times. The apparatus of the invention produces de-energizationof the drive motors in the display units successively as theyrespectively ground their contacts 52, until all drive motors have beende-energized, whereupon all display units start off together again. Theentire process takes place so rapidly that thehalting of the scriptsheets is hardly noticeable to the persons who read them.

For this synchronizing operation the control unit 2 includes for each ofthe di play units 4 directly controlled by it a sync control gridcontrolled gas discharge tube,

V203 and V303 in FIG. 2b, and a synchronizing relay having its actuatingcoil in series with the plate cathode conduction path of that tube. InFIG. 2b these relays are indicated at K202 and K302. A single one ofthese combinations only will be described.

Conductor 50 of one display unit, the left hand one in FIG. 2b, say,connects via the cable 3 of that display unit with a conductor 48 inunit 2. Conductor 48 connects, through a contact of the display unitdisconnecting switch, S201, to one end of a resistor R212 the other endof which connects, through a normally closed contact 202-3 of relayK202, with a conductor 56. All contacts of the switches S201 and S301are closed when those switches are positioned effectively to connecttheir display units 4 to the control unit 2.

Conductor 56 leads through a normally closed contact 103-2 of relay K203(FIG. 2a) to the junction of resistors R113 and R104 which are connectedin series between conductor as and ground. These resistors areproportioned to hold conductor 56 at cut-cit potential for tube V203when contact 1034 is closed.

The grid of tube V102 is connected to the same negative bias at thejunction of R113 and R104 through a resistor R106 of value largecompared with R2112. This grid is moreover additionally connectedthrough a conductor 58 and thence through switch $2011 to the end ofR212 adjacent conductor 56. The opposite end of R212, to which conductor40 connects, leads to the grid of V203 through a current limitingresistor R206.

Conductors S6 and 58 also connect, through contact 302-3 of relay K302and through switch S301 respectively to the end of a resistor R312 ofthe same value as R212 and forming part of an identical synchronizingcircuit for the right hand display unit 4 of FIG. 2b.

The display unit first to ground its contact 52 raises to zero bias thegrid of its sync control tube, V203 or V303, and so brings that tubeinto conduction, it being noted that the actuating coils of relays K202and K302 in the plate circuits of tubes V203 and V303 connect throughcontacts of switches S201 and S301 with the positive voltage conductors33 and 46 respectively.

With conduction in the sync control tube associated with the displayunit first to ground its synchronizing contact 52, V203 say, the relayK202 for that display unit will be energized.

Energization of relay K202 closes normally open contact 202-1 thereonthus lighting lamp 1201 to signify that the script in the left hand unithas come to a stop, as will presently be explained. In addition aholding circuit for K202 is established through V203 by grounding of thegrid of V203 through normally open contact 202-2, now closed. Opening ofnormally closed contact 202-3 opens the connection previously providedby relay K202, under control of the left hand display unit 4, betweenthe negative bias conductor 56 and conductor 58. In addition,energization of relay K202 opens at normally closed contact 2024 thereofthe armature circuit for motor 23 in the associated display unit 4,bringing the script in that display unit to a stop.

Negative bias voltage is still applied however from conductor 56 toconductor 50 and hence to the grid f tube V102 through the contact 302-3of the other display unit 4 of FIG. 2b which has not grounded itssynchro nizing contact 52 at a synchronizing discontinuity in the scriptsheet therein. When this second display unit grounds its contact 52,V303 will be brought into conduction, stopping the script motion in theassociated display unit and opening the connection between conductors 56and 50 provided by relay K302 when de-energized.

If additional display units are provided in the system for operationthrough an additional set or sets of the components shown to the left orright of the line A--A in box 2 of FIG. 2b, tube V102 will be heldbiased off until the synchronizing contact 52 has been grounded by ascript sheet discontinuity in all such additional display units. When,however, all display units have grounded their contacts 52 and haveconsequently effected energizetion of their associated relayscorresponding to relays K202 and K302 in FIG. 2b, the grid conductor 58to tube V102 will be disconnected from conductor 56 and will instead bereturned to ground potential through the paralleled resistors R212, R312and corresponding resistors of additional sets of display unit controlcomponents in the system, if any. Since these resistors are smallcompared to resistor 106. and since they are. in parallel, the grid oftube V102 will be brought substantially to ground potential and the tubewill conduct, producing energization of relay K103.

Opening of normally closed contact 103-1 of relay K103 disconnects fromground a conductor 60 in the common cathode circuit of sync controltubes V203, V303 and corresponding tubes in any additional sets ofdisplay unit control components which with their display units may beconnected in the system. This cuts off conduction in the sync controltubes and de-energizes synchronizing relays K202, K302 and correspondingadditional relays, if any, and hence reactivates the motors 28 in thescript display units. The script sheets accordingly start moving againin all display units, in the same direction as before, and with the sameline of text identically positioned in all at the viewing apertures inthe display units.

Opening of normally closed contact 103-2 on relay K103 disconnectsconductor 56 from its negative bias source. This prevents tube V102 frombeing returned to cut-off by connection of conductor 53 to conductor 55through the now again de-energized relays K202, K302 and the like.Instead, the grid of tube V102 is held at ground potential so long asany of the synchronizing contacts 52 is grounded by virtue of thevoltage divider constituted by R106 and the resistor corresponding toR212 at the display unit whose contact 52 remains so grounded, theresistors R212, R312 and the like being individually small compared toR106.

When the contacts 52 in both display units of FIG. 2b, and of otherdisplay units which may be included in the system, have beendisconnected from their rollers 54 by motion of their script sheets, thegrid of V102 will be returned to cut-off potential through R106. Thisdeenergizes relay K103, restores conductor 56 to cut-off potential andre-establishes the common cathode circuit for the sync control tubes.The control unit 2 is accordingly ready to synchronize the display units4 once more as soon as any one of them again grounds its contact 52.

Condenser C108 between ground and the grid of V102 prevents undesiredconduction in that tube due to transients or AC. pickup, and rectifiersZ203 and Z303 across the coils of relays K202, K302 act as aresuppressors.

Reference has already been made to the script reversing switches S401and S501. When open these switches, or rather the one thereofeifectively placed in circuit by the position of switch S502 and theconsequent condition of relay K101, places the voltage of conductors 24and 26 across lamp 1401 or 1501 to indicate that the circuit of controlunit 2 is set for forward direction of script travel. An open conditionof switches S401 and S501 correspondingly leaves relays K102 and K201de-energized. Closing of the operative one of switches S401 and S501instead short circuits lamp 140101" i501 and energizes relays K102 andK201.

If the direction of script movement were to be reversed by closing ofswitch S401 or S501 and consequent energization of relay K201 during thesynchronizing process, i.e. when any of the lamps, i201, 1301 or thelike is on, the script sheets might, with the circuit as thus fardescribed, be thrown out of synchronism to the extent of the separationof two adjacent discontinuities on the script sheets, the display unitshaving come to a stop synchronizing on one discontinuity and the otherson an adjacent discontinuity. This is prevented by a reverse releasecircuit comprising relay K102 (FIG. 2a) which is energized upon closingof either of the reversing switches S401 and S501.

Relay K102 has a set of single pole double throw contacts, one normallyclosed and one normally open, the movable contact blade of the setconnecting to the plate of V102. Each of the fixed contacts connects toground through a large capacitor, C or C106, shunted by a bleederresistor. Whenever the condition of energization of relay K102 ischanged upon change in direction of script travel, the plate of V102 isshifted to be connected to ground through that one of capacitors C105and C106 which has been allowed to discharge through its bleederresistor R111 or R112 during the interval of script travel precedingsuch reversal. The charging of the capacitor to the voltage on conductor38 eifects momentarily energization of relay K103 even though tube V102remains non-conducting. By cutting oti conduction in their sync controltubes such as V203 or V303 of the display units shown in FIG. 2b, suchenergization releases and restarts the script motors 28 in all displayunits which had stopped their script sheets when switch S401 or S501 wasshifted to effect the reversal of script travel in question.Accordingly, the armature circuit is maintained substantiallyuninterrupted for the drive motors in all display units and all displayunits immediately begin to move their script sheets in the oppositedirection. In this way it is insured that irrespective of the time ofreversal the next synchronizing cycle will take place in all displayunits at discontinuities similarly positioned with respect to the texton the script sheets therein.

A manually operable synchronizing release switch S102, spring-loaded toopen position, may be provided in parallel with V102. This switch, whenclosed, energizes K103, releasing all synchronizing relays such as K203or K303 which may have been operated. For example, when making scriptcorrections, the script sheets may be moved in a dissimilar manner inthe various display units so that synchronizing relays such as K203 orK303 are energized in some units 4 while the corresponding relays inother units 4 are not so energized. If the script sheets in such unitsare then manually returned to position the contacts 54 therein betweenthe same pair of adjacent discontinuities on their script sheets as inthe other display units and if switch S102 is then momentarily closed,proper synchronisrn will be re-established as soon as motorizedoperation is resumed by advancing of the speed control R401 or R501 to aposition at which armature current flows in the rectifier pairs such asV201,

, V202 and V301, V302.

In FIG. 2a there is shown in the master or ,selector hand control unit10 a two-conductor jack 9' inserted in series with potentiometer R501.The contacts of this jack are normally closed to complete the circuitfor potentiometer R501 between conductors 32 and 36. Upon insertion intothe jack of a plug at the endof cable 11 the foot switch 13 of FIG. 1 isinserted electrically into this circuit to permit start-stop operationof the systemfrom that foot switch, as already described. 7

Reference has already been made to the ability of the master controlcomponents of dash line box 2 in FIG. 2a to control sets of display unitcontrol components additional to the two such sets shown within box 2 inFIG. 2b, and through such additional sets, additional display units 4 topermit the assembly of a cuing system according to the inventionincluding more than two display units. This may be done either (as shownin FIG. 4) by means of separate units or chassis duplicating thecomponents of box 2 in FIG. 2b or (as shown in FIG. by means of one ormore additional complete control units 2. To permit the assembly of sucha cuing system the control unit 2' is provided with a number ofconnectors.

It will be observed that the signals passing between the master controlcomponents of box 2 in FIG. 2a and the two sets of display unit controlcomponents of box 2 in FIG. 2b are carried by six conductors. Thesecomprise a conductor 68 between switch S401 or S501 and the actuatingcoil of relay K201, a conductor 70' between the cathode of V101b and thegrid circuits of V201, V202 and V301, V302, a conductor 72 in serieswith themaster script light switch S103, and the conductors 60, 56 and58 already discussed. The A.C. supply voltage is passed from FIG. 2a toFIG. 2b by conductors 24 and 26 and, in the particular embodimentillustrated a rectified supply voltage for the sync release tube V102 ispassed from FIG. 2b to FIG. 2a by a conductor 38.

To permit the inclusion of additional display units in the cuing systemof FIGS. 2a, 2b by duplication of the display unit control components ofFIG. 2b, the signalcarrying conductors 68, 70, 72, 60, 56 and 58, aconductor 74 establishing at system ground potential the chassis groundsof FIGS. 2a and 2b and also the A.C. power conductors 24 and 26 requiredfor energization of such a duplication of the components of box 2 inFIG. 2b are brought out to a connector or socket 76 shown in FIG. 2b. Acable with a suitable plug may be fitted into connector 76 to terminatein a chassis (not shown in FIG. 2a, 2b) duplicating the components ofbox 2 in FIG. 2b, thus permitting synchronized operation of as many asfour display units. If such a chassis, duplicating the components of box2 in FIG. 2b, itself includes a socket the pins or conductors of whichare in parallel with those of the cable last mentioned, the conductors68, 70, 72, 74, 60, 56, 58, 24 and 26 of FIGS. 21: and 2b may beextended from that chassis through a further cable to still anotherchassis duplicating a second time the components of box 2 in FIG. 2b,and so on up to the limit of load which the master control components ofFIG. 2a can sustain.

FIG. 4 is a diagrammatic showing of a cuing system according to theinvention capable of effecting synchronizcd operation of as many as sixdisplay units. Five are there shown. In FIG. 4 a control unit is shownat 2, with cables 3 connecting to two display units 4 and with cables I2and 14 connecting to control units 8 and 10 in the same manner as shownin FIG. 1. The control unit 2 of FIG. 4 is indicated at its right-handside as including a socket '76 as above mentioned, into which there fitsa plug 73 whose cable 80 connects into achassis 82 which duplicates thecomponents shown within box 2 in FIG. 2b. This unit 82, which may betermed a cuing control unit to distinguish it from the complete controlunit 2, is electrically identical with the components within box 2 inFIG. 2b. It is coupled by two cables 3 to the third and fourth displayunits 4 of the system of FIG. 4. Going control unit 82 includes a socket76 into which fits the plug 78 of another cable 80 terminating at asecond cuing control unit 82, shown in FIG. 4 as controlling a singledisplay unit 4. I

To permit the assembly of a cuing system capable of eiiectingsynchronized operation of more than two display units by using two ormorecomplete control units 2, as diagrammatically indicated in FIG. 5,provision is made whereby upon such combination of two complete controlunits 2 there may be energized the master control components of only oneof these two control units 2. To this end the conductors 68, 70, 72, 74,60, 56, 58, 24 and 26 are extended within each control unit 2 from themaster control components of box 2 in FIG. 2a to the display unitcontrol components of box 2 in FIG. 215 via a detachable cable 88.Conductor 38 may be omitted from cable 88 and permanently wired betweenthe actuating coil of relay K103 and the output of rectifier combinationZ201, Z202. While this arrangement will, in a cuing system such as thatof FIG. 5, apply plate voltage to the sync release tube V102 in controlunits 2 which are being employed for their display unit controlcomponents only, such as the lower control unit 2 in FIG. 5, this iswithout effect on the system and entails no power drain since thefilament of that tube will not be energized. Filament circuits have forsimplicity been omitted from FIGS. 2a and 2b. They are preferably soarranged however that the filaments of tubes in FIG. 2a are energizedfrom windings 011 transformer T101. 1 The filaments of the tubes in FIG.2b to the left andright of line A-A, belonging to the two sets ofdisplay unit control components of FIG. 2b, are energized from windingson transformers T201 and T301 respectively. These conductors arebrought,

1 1 from their related circuit elements in FIG. 2a, to a socket 34- intowhich fits a plug 36 at one end of a nine conductor cable 88 whose otherend extends these conductors to their related circuit elements in FIG.2b.

Whenever a control unit 2 is to function for the overall control ofcuing system, AC. power is fed to it at its jack 5, and its master anddisplay unit control components are interconnected via the cable 88 asabove described. This is the arrangement illustrated for the singlecontrol unit 2 of FIG. 4.

In FIG. 5, the upper control unit 2 is serving to operate the systemthere illustrated, and its master and display unit control componentsare accordingly interconnected by a plugging of the cable 88 of thatunit into connector 84 of that unit. The lower control unit 2 of FIG. 5is however being used only for its display unit control components.Consequently that unit receives no power at its power input jack 5, andits cable 88 instead of being connected to the connector 84 of its ownmaster control components, is connected to the connector 7 6 of theupper control unit 2.

Of course, the sets of display unit control components need not beprovided in pairs, either in the unit 2 of FIG. 211 or in the unit 82 ofFIG. 4. Instead, they may be assembled in separate units including onlythose components to the left or right of the line AA within box 2 inFIG. 2b, such a chassis however including a source of field excitationvoltage such as transformer T262 and one of the rectifier combinationsZ201, Z202 or Z301, Z302 and also a reversing relay such as K201 withone of the sets of contacts thereof. In FIG. 2b it is simply for reasonsof economy and simplicity that both rectifier combinations are fed froma single transformer and that a single relay K101 operates the fieldcircuit reversing contacts for the two sets of display unit controlcomponents to the left and right of the line AA. Indeed the packaging ofthe components of a system according to the invention may be verydifferent from that which has been shown and described herein. Thus thesets of display unit control components may be physically associatedwith the display units which they control. Usually, however, it isdesirable to make the display units as light and compact as possible andhence to dispose the display unit control components elsewhere.

The invention may be embodied in apparatus differing in other ways fromthat which has been shown and described herein, the invention itselfbeing set forth in the appended claims.

I claim:

1. Cuing apparatus comprising a plurality of script display means and acontrol means, each of said display means including a motor, a scriptsheet having a plurality of discontinuities disposed lengthwise thereof,means coupling said script sheet to said motor, a conductor, and aswitch operable upon passage of each of said discontinuities past alocation fixed with reference to said coupling means, said control meansincluding for each of said display means an electron discharge tubecontrolling, according to its state of conduction, the application ofpower to the motor in the associated one of said display means, andmeans responsive to operation of the associated one of said switches tochange the state of conduction in the associated one of said tubes, saidcontrol means further including for said display means collectively anelectron discharge device controlling, according to its state ofconduction, the state of conduction in said tubes, and means to changethe state of conduction in said device responsive to change in the stateof conduction in all of said tubes by operation of their respectiveswitches.

2. Cning apparatus comprising a plurality of script display means and acontrol means, each of said display means including a motor, a scriptsheet having a plurality of discontinuities disposed lengthwise thereof,means coupling said script sheet to said motor, a conductor, a

switch operable upon passage of each of said discontinuities past alocation fixed with reference to said coupling means, said control meansincluding for each of said display means an electron discharge tubecontrolling, according to its state of conduction, the application ofpower to the motor in the associated one of said display means, andmeans responsive to operation of the associated one of said switches tochange the state of conduction in the associated one of said tubes, saidcontrol means further including for said display means collectively anelectron discharge device cont-rolling, according to its state of conduction, the state of conduction in said tubes, means to change thestate of conduction in said device responsive to change in the state ofconduction in all of said tubes by operation of their respectiveswitches, and means to hold said device in its state of conduction sochanged so long as any of said switches is operated.

3. Cning apparatus comprising a plurality of script display means and acontrol means, each of said display means including a motor, a scriptsheet having a plurality of discontinuities disposed lengthwise thereof,means coupling said script sheet to said motor, a conductor, and aswitch operable upon passage of each of said discontinuities past alocation fixed with reference to said coupling means, said control meansincluding for each of said dis play means an electron discharge tubepermitting, when non-conducting, application of power to the motor inthe associated one of said display means, and means responsive tooperation of the associated one of said switches to bring said tube intoconduction, said control means further including for said display meanscollectively an electron discharge device permitting, whennon-conducting, conduction in said tubes, and means responsive toconduction in all of said tubes to establish conduction in said device.

4. Cuing apparatus comprising a plurality of script display means and 'acontrol means, each of said display means including a motor, a scriptsheet having a plurality of discontinuities disposed lengthwise thereof,means coupling said script sheet to said motor, a conductor, a switchoperable upon passage of each of said discontinuities past a locationfixed with reference to said coupling means, said control meansincluding for each of said display means an electron discharge tubepermitting, when nonconducting, application of power to the motor in theassociated one of said display means, and means responsive to operationof the associated one of said switches to bring said tube intoconduction, said control means further including for said display meanscollectively an electron discharge device permitting, whennon-conducting, conduction in said tubes, means responsive to conductionin all of said tubes to establish conduction in said device, and meansresponsive to conduction in said device to prevent conduction in saidtubes so long as any of said switches is operated.

5. Cuing apparatus comprising a plurality of script display means and acontrol means, each of said display means including a motor, a scriptsheet having a plurality of discontinuities disposed lengthwise thereof,means coupling said script sheet to said motor, a conductor, and meansto connect said conductor to a common point of fixed potential uponpassage of each of a plurality of discontinuities in said script sheetpast a display station, said control means including for each of saiddisplay means an electron discharge tube effecting, when nonconducting,application of power to the motor in the associated one of said displaymeans, and means responsive to connection of said conductor to saidpoint of fixed potential to bring said tube into conduction, saidcontrol means further including for said display means collectively asource of bias voltage negative with respect to said fixed potential,and an electron discharge device permitting, when non-conducting,conduction in said tubes and application of said bias voltage to saidtube individually. and to said device through parallel circuitscompleted one for each of said tubes when non-conducting, whereby saiddevice is rendered conducting in response to conduction in all of saidtubes andsaid tubes are thereupon extinguished. t

6. Cuing apparatus comprising a plurality of script display means and acontrolmeans, each of said display means including a motor coupled to ascript sheet,a conductor, and means to connect said conductor to a common point of fixed potential upon passage of each of a plurality ofdiscontinuities in said script sheet past a display station, saidcontrol means including for each-of said display means an electrondischarge tube having cathode, anode and control electrodes, and meansresponsive to connection of said conductor to said point of fixedpotential to bring said tube into conduction, said control means furtherincluding, for said display means collectively, a source of bias voltagenegative with respect to said fixed potential, and an electron dischargedevice having anode, cathode and control electrodes, each of said tubes,when non-conducting, effecting application of power to the motor in theassociated one of said display means and permitting connection of saidnegative bias voltage through a separate circuit to the controlelectrode of said electron discharge device, said discharge devicepermitting, ,when non-conducting, conduction in said tubes andconnection of said source of negative voltage to the inputs to saidseparate circuits, said control means further including for each of saiddisplay units means connecting said conductor to the control gridof'said device through a resistance.

7. Cuing apparatus comprising a plurality of script display means eachincluding a motor coupled to a script sheet, a conductor, and means toconnect said conductor to' a common point of fixed potential uponpassage of each of a plurality of discontinuities in said script sheetpast a display station, said apparatus further comprising a controlmeans including for each of said'display means an electron dischargetube having anode, cathode and control grid electrodes, a relay actuableupon conduction in said tube, said relay controlling application ofpower to said drive motor, a resistor in the grid circuit of said tube,means connecting said conductor to the grid side of said resistor, saidcontrol means further including for said display means collectively anelectron discharge device having anode, cathode and control gridelectrodes, a source of cut off bias voltage for said device and tubesnegative with respect to said fixed potential, a largeresistorconnecting the control grid of said device to said source, a relayactuable upon conduction in said device, firstconducting meansconnecting the control grid of said device to the ends of all of saidfirst-named resistors remote from the grid circuits of said tubes,second conduoting means connecting said source to said first conductingmeans through contacts on said last-named relay and through contacts onall of said first-named relays, and third conducting means completingthe external anode cathode paths of said tubes through contacts of saidlastnamed relay. p i r 8. Cuing apparatus comprising a plurality ofscript display means each including a motor coupled to a script sheet, aconductonand means to connect said conductor to a common point of fixedpotential upon passage of each of a plurality of discontinuities in saidscript sheet past a display station, said apparatus further comprising acontrol means including for each of said display means an electrondischarge tube having anode, cathode and control grid electrodes, arelay actuable upon conduction in-saicl tube, said relay controllingapplication of power to said drive motor, a resistor in the grid circuitof said tube, means connecting said conductor to the grid side of saidresistor, said control means further including for said display meanscollectively an electron discharge device having anode, cathode andcontrol grid electrodes, a source of cut ofi bias voltage for saiddevice and tubes negativewith respect to said fixed potential, a largeresistor connecting the control grid of said device to said source, arelay actuable upon conduction in said device,

first conducting means connecting the control grid of said device to theends of all of said first-named resistors remote from the grid circuitsof said tubes, second conducting means connecting said source to saidfirst conducting means through contacts on said last-named relay andthrough contacts on all of said first-named relays, and third conductingmeans completing the external anodecathode paths of said tubes throughcontacts of said lastnamed relay.

9. A cuing system comprising a plurality of display means and a controlmeans, each of said display means including a direct current motor, ascript sheet having a plurality of discontinuities disposed lengthwisethereof, means coupling said script sheet to said motor, said controlmeans including for each of said display means a grid controlledrectifier connected between a source of voltage alternating with respectto a point of fixed poten* tial and one end of a driving circuit of saidmotor the other end of which connects to said point of fixed potential,said control means further including means to superimpose on a variablevoltage unidirectional with respect to said fixed potential asubstantially saw-tooth shaped voltage having a repetition rate of twicethe frequency of said alternating voltage, and means to apply a voltagerepresentative of the sum of said saw-tooth and unidirectional voltagesbetween the control grids of said rectifiers and said point of fixedpotential.

10. A cuing, system comprising a pluralityof display means and a controlmeans, each of said'display means including a direct current motor, ascript sheet having a plurality of discontinuities disposed lengthwisethereof, means coupling said sheet to said motor, said control meansincluding for each of said display means a grid controlled rectifierconnected between a source ofvoltage alternating with respect to a pointof fixed potential and one end of a driving circuit of said motor theother end of which is connected to said point of fixed potential, aparallel resistance-capacity circuit in series with the control grid ofsaid rectifier, and a voltage divider circuit into which said parallelcircuit is tapped, said control means further including means tosuperimpose on a variable voltage unidirectional with respect to saidfixed potential a substantially saw-tooth shaped voltage having a repetition rate of twice the frequency of said alternating voltage, and meansto apply across said voltage divider circuits a voltage representativeof the sum of said saw-tooth and unidirectional voltages.

11. A cuing system comprising a plurality of script display means and acontrol means, each of said display means including a' direct currentmotor, said control means including means to generate from analternating current voltage a substantially saw-tooth shaped voltagehaving a repetition rate of twice the frequency of said alternatingvoltage and means to superimpose said saw-tooth voltage on a voltage ofadjustable value and fixed polarity with respect to a point of fixedpotential, said control means further including for each of said displaymeans a grid controlled gas discharge tube having anode, cathode andcontrol grid electrodes, said tube having its anodecathodejpathconnected between a source of alternating current potential of saidfrequency and one end of a driving circuit for said motor the other endof which is connected to said point of fixed potential, said controlmeans further including for each of said display means a parallelcombination of resistance and capacity connected in series with thecontrol grid circuit of said'tube, and

means to apply a voltage representative of the sum of said saw-tooth andvariable direct current voltages between the end of said parallelcircuit remote from said control grid and said point of fixed potential.i

12. A cuing system comprising a plurality of script display means and acontrol means, each of said display means including a direct currentmotor, said control means including means to generate from analternating current voltage a' substantially saw-tooth shaped voltagehaving a repetition rate of twice the frequency of said alternatingvoltage and means to superimpose said sawtooth voltage on a voltage ofadjustable value and fixed polarity with respect to a point of fixedpotential, said control means further including for each of said displaymeans a grid controlled gas discharge tube having anode, cathode andcontrol grid electrodes, said tube having its anode-cathode pathconnected between a source of alternating current potential of saidfrequency and one end oi the armature circuit of said motor the otherend of said armature circuit connecting to said point of fixedpotential, said control means further including for each of said displaymeans a parallel combination of resistance and capacity connected inseries with the control grid circuit of said tube, and means to applythe sum of said saw-tooth and variable direct current voltages betweenthe ends of said parallel circuits remote from said control grid andsaid point of fixed potential.

13. A cuing system comprising a control unit and a plurality of scriptdisplay units, each of said display units including a reversible scriptdriving motor adapted to be coupled to a script sheet and means todevelop a signal at spaced points along said sheet as moved by saidmotor past a display station, said control unit including in each ofsaid display units a pair of grid controlled gas discharge rectifiertubes driven in opposite phase on their plates from a source ofalternating current potential, said tubes having their anode-cathodepaths connected in parallel in the armature circuit of one of saidmotors, the tubes of each of said pairs having in a common grid circuita parallel combination of resistance and capacity, said control circuitincluding means to apply between the ends of said parallel circuitsremote from the grids of said rectifier pairs and a point of fixedpotential a substantially sawtooth voltage of twice the frequency ofsaid alternating current potential superimposed on an adjustable directcurrent voltage.

14. A cuing system comprising a plurality of script display means and acontrol means, said display means including each a script driving motorcoupled to a script sheet, a conductor, and means to connect saidconductor to a point of common fixed potential upon passage past adisplay station of each of a plurality of discontinuities disposedlengthwise of said sheet, said control means including for each of saiddisplay units an electron discharge device having anode, cathode andcontrol grid electrodes, a relay actuable upon conduction in saiddevice, and a resistor connected between said conductor and one of afirst pair of contacts of said relay closed for the non-conductingcondition of said device, said relay including further contacts whichfor the non-conducting condition of said device complete the energizingcircuit of said motor, said conductor leading to the grid circuit ofsaid device, said control means further including an electron tubehaving anode, cathode and control electrodes, a relay actuable uponconductoin in said tube, a source of cut off bias voltage for saiddevices and tube negative with respect to said fixed potential, meansincluding a large resistor connecting the control electrode of said tubeto said source, first conducting means connecting said source to theother contact of each of said first pairs of contacts, second conductingmeans connecting the control grid of said tube with each of said onecontacts of said first pairs of contacts and a third conducting means inthe cathode circuits of said devices, said last-named conducting meansincluding contacts in the relay actuable upon conduction in said tube,said lastnamed contacts being closed for the nonconducting condition ofsaid tube.

15. A cuing system comprising a plurality of script display means and acontrol means, said display means including each a script driving motorcoupled to a script sheet, a conductor, and means to connect saidconductor to a point of common fixed potential upon passage past radisplay station of each of a plurality of discontinuities disposedlengthwise of said sheet, said control means iniii eluding for each ofsaid display means an electron discharge device having anode, cathodeand control grid electrodes, a relay energizable upon conduction in saiddevice, and a resistor connected between said conductor and one of afirst pair of normally closed contacts of said relay, said relayincluding further normally closed contacts in the energizing current ofsaid motor, said conductor leading to the grid circuit of said device,said control means further including an electron tube having anode,cathode and control electrodes, a relay energizable upon conduction insaid tube, a source of cut off bias voltage for said devices and tubenegative with respect to said fixed potential, means including a largeresistor connecting the control electrode of said tube to said source,first conducting means connecting said source to the other contact ofeach of said first pairs of contacts through normally closed contacts ofsaid last-named relay, second conducting means connecting the controlgrid of said tube with each of said one contacts of said first pairs ofcontacts, and a third conducting means in the cathode circuits of saiddevices, said last-named conducting means including normally closedcontacts on said last-named relay.

16. Cuing apparatus comprising a plurality of script display means and acontrol means therefor, each of said display means including a motor fordriving past a display station a script sheet having discontinuitiesdisposed lengthwise thereof and a switch actuable by saiddiscontinuities successively, said control means comprising an electrondischarge tube having anode, cathode and control grid electrodes, asource of cut off bias voltage, means including a resistor connectingthe control grid of said tube to said source, a relay actuable uponconduction in said tube to open two pairs of contacts of said relay,said apparatus further comprising, for each of said units, an electrondischarge device having anode, cathode and control grid electrodes, arelay actuable in response to conduction in said device to open twopairs of contacts of such relay of which one is in the energizingcircuit of said motor, the control grid of said device being connectedto said source through a resistor smaller than said first-named resistorand through the other of said last and one of said first named pairs ofcontacts, means responsive to actuation of said switch to bring saiddevice in the conduction, means connecting the control grid of said tubeto the ends of said last-named resistors remote from the control gridsof said devices, and means completing the external anode, cathodeconduction paths of said devices through the others of said first-namedpairs of contacts.

17. A cuing system comprising a plurality of script display units eachincluding an electric motor coupled to a script sheet and means todevelop a signal at spaced points along said script sheet as moved bysaid motor past a display station, said cuing system further comprisinga control unit including for each of said display units two gridcontrolled gas rectifiers connected in the armature circuit of saidmotor and driven in opposite phase on their plates from a source ofalternating current voltage, a parallel resistance-capacity circuit inthe common grid circuit of said rectifiers, a relay through a first pairof normally closed contacts of which passes the armature circuit of saidmotor, a gas triode having its plate-cathode conduction path in serieswith the activating coil of said relay, a resistor in the grid circuitof said triode, means to apply said signals as unbiasing signals betweensaid resistor and the control grid of said triode, said control unitfurther including for said display units collectively means to generate,on a direct current voltage of variable value, a substantially saw-toothshaped voltage at twice the frequency of said alternating currentvoltage and to apply the sum of said variable and saw-tooth voltagesbetween a point of fixed potential and the ends of said parallelcircuits remote from the grids of said rectifiers, a gastriode tube, arelay energizable upon conduction in said tube, a resistor of largervalue than said first-named resistors coupling the control grid of saidtube to a source of cut off bias, conducting means connecting saidsource through a second pair of normally closed contacts on each of saidfirst-named relays to the ends of said firstnamed resistors remote fromthe grids of their associated gas triodes, conducting means including asecond pairof normally closed contacts on said last-named relay in thecathode circuits of all of said gas triodes, and conducting meansconnecting the control grid of said tube to the ends of said smallresistors remote from the grids of their associated gas triodes.

18. A cuing system comprising a plurality of script display units eachincluding an electric motor coupled to a, script sheet "and means todevelop a signal at spaced points along said script sheet as moved bysaid motor past a display station, said cuing system further comprisinga control unit including for each of said display units two gridcontrolled gas rectifiers connected in the armature circuit of saidmotor and driven in opposite phase on their plates from a source ofalternating current voltage, a parallel resistance-capacity circuit inthe common grid circuit of said rectifiers, a relay through a first pairof normally closed contacts of which passes the armature circuit of saidmotor, a gas triode having its plate-cathode conduction path in serieswith the actuating coil of said relay, a resistor in the grid circuit ofsaid triode, means to apply said signals as unbiasing signals betweensaid resistor and the control grid of said triode, said control unitfurther including for said display units collectively means to generate,on a direct current voltage of variable value, a substantially saw-toothshaped voltage at twice the frequency of said alternating currentvoltage and to apply the sum of said variable and saw-tooth voltagesbetween a point of fixed potential and the ends of said parallelcircuits remote from the grids of said rectifiers, a gas triode tube, arelay energizable upon conduction in said tube, a resistor of largervalue than said first-named resistors coupling the control grid of saidtube to a source of cut off bias, conducting means connecting saidsource through a first pair of normally closed contacts on saidlast-named relay and through a second pair of normally closed contactson each of said first-named relays to the ends of said first-namedresistors remote from the grids of their associated gas triodes,conducting means including a second pair of norm-ally closed contactsonsaid last-named relay in the cathode circuits of all of said gastriodes, and conducting means connecting the control grid of said tubeto the ends of said small resistors remote from the grids of theirassociated gas triodes.

References Cited in the file of this patent UNITED STATES PATENTS2,359,014 Ward Sept, 26, 1944 2,422,149 Unkles June 10, 1947 2,444,796Whalley July 6, 1948 2,737,619 Shank Mar. 6, 1956 2,737,622 Jelinck Mar.6, 1956 2,760,137 Andrews Aug. 21, 1956 2,780,763 Hertwig Feb. 5, 19572,799,820 Gutterman July 16, 1957 2,848,671 McDonald Aug. 19, 1958

